Playing devil's advocate: if Word 97 (or something even older like wordperfect) does all you need, why should you upgrade?
Things are different, of course, when you have to interoperate with other people (in the word processor case, mainly by reading files written by other people); not only do security fixes become more relevant, but also newer versions of the software have greater compatibility (in the word processor case, not only there was a lot of work on libreoffice towards better compatibility with Microsoft document formats, but also AFAIK newer libreoffice versions write by default using a newer version of the OpenDocument formats, so if you have an outdated word processor, you might have difficulty reading files written by other people using these newer versions).
Playing devil's advocate: if Word 97 (or something even older like wordperfect) does all you need, why should you upgrade?
Things are different, of course, when you have to interoperate with other people (in the word processor case, mainly by reading files written by other people); not only do security fixes become more relevant, but also newer versions of the software have greater compatibility (in the word processor case, not only there was a lot of work on libreoffice towards better compatibility with Microsoft document formats, but also AFAIK newer libreoffice versions write by default using a newer version of the OpenDocument formats, so if you have an outdated word processor, you might have difficulty reading files written by other people using these newer versions).